The present invention relates to a coating film forming method and a coating apparatus capable of forming a liquefied coating film by virtue of a solvent such as a resist film, for example, on a surface of a liquid crystal display (LCD) substrate or a semi-conductor wafer.
In manufacturing the LCD substrate, for example, circuits can be formed by coating photoresist on the LCD substrate, then transferring circuit patterns onto the photoresist in terms of a photolithography technique, and then developing the photoresist. In these steps, a coating film forming step of supplying a coating liquid on a surface of the substrate is included.
In this case, as a method of forming a resist film, such a method has been known that, for example, a rectangular LCD substrate is loaded and fixed on a loading table provided in a processing vessel, then an opening portion of the processing vessel is closed by a lid member, then the processing vessel and the loading table are rotated together, then a resist liquid (coating liquid) consisting of a solvent and a photosensitive resin is dropped onto a center area of an upper surface of this substrate, and then the resist liquid is spread in a spiral fashion from a center portion of the substrate to a peripheral portion thereof by virtue of a rotating force and a centrifugal force of the substrate to thus be coated on the upper surface.
In this method, the resist liquid can be coated on the substrate by spreading the resist liquid from a center portion of the substrate to a peripheral portion thereof while rotating the substrate, so that a considerable amount of resist liquid has been scattered toward the processing vessel from an outer peripheral portion which has an extremely high peripheral velocity rather than the center portion thereof. In this case, out of the dropped resist liquid, an amount of the resist liquid coated on the substrate has 10 to 20%, and remaining 80 to 90% has scattered toward the processing vessel.
In particular, in the event that the resist liquid is coated on the rectangular LCD substrate, a very large quantity of the resist liquid has been wasted in order to coat the resist liquid on the overall surface of the substrate without surface areas left uncoated. In recent years, an increase in size of the LCD substrate has been progresses and as a result the waste of the resist liquid has been accelerated in the prior art.